Insomnia is a complaint that sleep is difficult to initiate or maintain, or that it is not refreshing or restorative. A person that suffers from insomnia has difficulty falling asleep or staying asleep, or wakes too early. As a consequence, insomnia sufferers begin to dread not only each night of sleeplessness but also the fatigue, mental clouding, and irritability of the coming day.
Insomnia is a widespread problem. For example, a study conducted in the United States revealed that more than 50% of the respondents reported having experienced at least one of the following symptoms of insomnia at least a few nights a week: difficulty falling asleep, waking often during the night, waking up too early and not being able to get back to sleep, and waking up feeling unrefreshed. In fact, 35% of the respondents said that they experienced at least one of these four symptoms of insomnia every night or almost every night. Extrapolating these study statistics to the United States Census data at the time the study was conducted suggests that over 120 million U.S. adults experience at least one of the four symptoms of insomnia at least a few nights every week. Of this 120 million, over 70 million experience these symptoms every night or almost every night. The direct economic costs of insomnia in the U.S. are estimated at close to $14 billion annually. The amount spent on over the counter medications and “alternative” treatments such as herbal remedies may double this estimate.
Nonpharmacologic behavioral therapies have achieved significant success in treating insomnia. Behavioral therapies have many advantages over pharmacologic therapies, including:                No risk of tolerance, dependence or side effects.        Correcting core behavior instead of treating symptoms.        Documented safety and effectiveness.There are a number of nonpharmacologic behavioral therapies that have been found to be effective for the treatment of insomnia. Those that have been most extensively evaluated are stimulus control therapy, sleep restriction therapy, relaxation training and paradoxical intention. Among these therapies, no techniques have been found to be more effective than stimulus control therapy.        
Stimulus control therapy is based on the premise that insomnia is a conditioned response to temporal (bedtime) and environmental (bed/bedroom) cues that are usually associated with sleep. Accordingly, the main objective of stimulus control therapy is to reassociate the bed and bedroom with rapid sleep onset by curtailing overt and covert sleep incompatible activities that serve as cues for staying awake and by enforcing a consistent wake and sleep schedule. Stimulus control therapy may be characterized as consisting of the following instructional procedures:                1. Use the bed and bedroom only for sleep (sexual activity is the only exception to this rule);        2. When you get into bed, turn out the lights with the intention of going right to sleep;        3. If you find yourself unable to fall asleep within a brief period of time (e.g. 15 to 20 minutes), then get out of bed and leave the bedroom. Stay up as long as you wish and then return to the bedroom when ready to sleep;        4. If you still cannot fall asleep, repeat step 3. Do this as often as is necessary throughout the night;        5. Maintain a regular wake time in the morning regardless of sleep duration the previous night, and        6. Avoid daytime napping.        
Another nonpharmacologic behavioral approach to treating insomnia, sleep restriction therapy, consists of curtailing the amount of time spent in bed to more nearly match the subjective amount of time asleep. For example, if a person reports sleeping an average of 5 hours per night out of 8 hours spent in bed, the initial prescribed sleep window (i.e., from bedtime to arising time) would be 5 hours. Subsequently, the allowable time in bed is increased by 15-20 minutes for a given week when sleep efficiency (ratio of total sleep time to the total time spent in bed) exceeds 0.9, decreased by the same amount of time when sleep efficiency is lower than 0.8, and kept stable when sleep efficiency falls between 0.8 and 0.9. Adjustments are made periodically (usually on a weekly basis) until the desired sleep duration is achieved. Sleep restriction therapy promotes a more rapid sleep onset, higher sleep efficiency, and less inter-night variability. Also, to prevent excessive daytime sleepiness when implementing sleep restriction therapy, it is generally recommended that time in bed should not be less than 5 hours per night.
Those behavioral techniques for treating insomnia that require self-assessment of sleep parameters (such as sleep onset latency, total time asleep, total time awake after sleep onset, sleep efficiency, etc.) could be significantly enhanced if the burden of consciously keeping track of sleep parameters is relegated to an automated system. For example, with current approaches to sleep restriction therapy, the patient is required to note the amount of sleep achieved each night and manually calculate their average time asleep and average sleep efficiency for each week. Given the tendency for a person suffering from insomnia to grossly underestimate their time asleep, they could unnecessarily begin the program with an overly restrictive sleep schedule, thereby reducing compliance by making the regimen less tolerable. Furthermore, the patient would need to continually reevaluate their sleep parameters and adjust their sleep schedule as appropriate.
Central to the automation of behavioral therapies for insomnia is the determination of sleep parameters. The determination of sleep parameters requires wake/sleep determination, that is, a determination as to whether the subject is awake or asleep, as those terms are understood by those skilled in the art. The known techniques for determining wake/sleep states fall into two broad categories, determined from the perspective of the subject using the device, either active or passive. A device that relies upon the subject to perform an action in order to determine whether they are awake or asleep is considered an active device. An active device could require, for example, that the subject respond to an audio tone with a button press or could require holding down the plunger of a dead mans switch in order to infer/determine whether the subject is awake or asleep at any given instant in time. By contrast, a passive device would require no action on the part of the subject to determine whether they are awake or asleep. A passive device, for example, could use electroencephalographic (EEG) signals to indicate the wake or sleep state, and this would not require any action on the part of the subject in making this determination.
There are advantages and disadvantages to both categories of devices. Probably the single biggest advantage of the active devices over passive is their relative simplicity. For example, monitoring the contact status of a dead mans switch (an active device) is much simpler and more straightforward than trying to determine changes in the wake/sleep state using EEG analysis (a passive device).
In 2002, Riley, W., et al., in an abstract entitled Initial Evaluation of a Computerized Behavioral Intervention for Primary Insomnia from the 36th Annual Convention of the Association for the Advancement of Behavior Therapy in Reno, Nev., described a behavioral therapy for insomnia that required wake/sleep state information. Their approach used an active device that produced a low volume auditory beep every 10 minutes to which the subject was required to respond. This presentation of the beep and the subsequent response (or lack thereof) was used to determine the wake/sleep state of the subject. Active methods of wake/sleep determination, such as this, are not truly automatic and have many drawbacks, including the following:                (1) A continuous presentation of stimuli (beeps) can produce undue task loading of the subject. If the subject is tasked with responding to very frequent stimuli, then the device itself can interfere with the process of falling asleep. On the contrary, if the stimuli are presented too infrequently, then the time localization of the wake/sleep determination could become too inaccurate because of the temporal granularity. Long time intervals between successive stimuli provide an opportunity for the subject to fall asleep but are at odds with the device's need for current information about the subject's wake/sleep status. For example, with the presentation of successive stimuli every 10 minutes, the device does not know what happened during the intervening time; the subject could have fallen asleep and awoken during the interval, etc. This could negatively impact the implementation of a behavioral therapy.        (2) The stimuli used in the active device of Riley et al. has the potential of being missed by the subject if it is of low amplitude, or it could wake the subject if the amplitude is too high. Alternatively, an active device employing a small amplitude vibratory stimulus could be missed, and a large amplitude vibratory stimulus could wake the subject. The same drawbacks apply to other types of stimuli used in active devices.        
(3) When using an active device, the subject will be at a more heightened level of vigilance and may also be encumbered with having to perform a task. As a result, the subject cannot simply relax in bed and passively rely on the device. Active devices can be especially detrimental to insomniacs because sleep time for insomniacs is more stressful than for people without sleep problems. While tasks required of anyone trying to fall asleep would have a negative impact on sleep, this is especially so in insomniacs. Even a task as simple as depressing the plunger of a dead mans switch would necessitate a higher level of vigilance (i.e. making sure they continue holding down the switch) during a time when they should be relaxing and drifting off to sleep.                (4) Some active methods could awaken a bed partner, particularly if they use visual or audible stimuli.        (5) Methods that employ switch contacts suffer from the inability to reengage automatically when the subject wakes. Because of this, they can only detect the first episode of sleep onset. A person suffering with insomnia could also have trouble falling back to sleep after waking during the night, or, perhaps they may simply have trouble staying asleep. A dead mans switch, for example, would have to be reengaged by the subject in order for the device to redetermine the next period of sleep onset after waking. These methods would be extremely cumbersome to use for most normal sleepers and would be especially difficult for someone with highly disrupted sleep.        
Active wake/sleep determination methods have also been described for other applications including the following:
MacLean U.S. Pat. No. 5,259,390 describes a hand mounted vibrating stimulus-response device to monitor sleep behavior. This device is intended for in-home prescreening of sleep before a full polysomnogram is given. It determines wake and sleep states by requiring the subject to press the response button each time they feel the vibratory stimulus.
Wyatt et al. U.S. Pat. No. 6,078,549 is directed to a sleep pattern timer using a plurality of switches to record parameters such as time before sleep onset, sleep time, etc. This device is used to assist in the diagnosis and treatment of sleep disorders by requiring the subject to hold switch(s) in a closed position and then release when the subject falls asleep.
Wyatt U.S. Pat. No. 6,392,962 entails a method of providing information to aid in the treatment of sleep disorders that would otherwise be difficult because of an insomniac's underestimation of total sleep time and/or overestimation of the time necessary to fall asleep. The apparatus, which includes a wrist-mounted timer with a hand mounted actuator, stops timing when the insomniac falls asleep and this disengages contact with the actuator. It is intended for wake/sleep determination (at sleep onset), and to correct an insomniac's overestimation of sleep latency and underestimation of total sleep and sleep efficiency.
To the knowledge of the present inventors, passive methods of determining wake/sleep have not been used or suggested to automate the implementation of behavioral sleep therapies. Such methods can determine the wake/sleep state of the subject without the need of any action on the part of the subject or the presentation of response inducing stimuli. Examples of devices that may be used to passively determine wake/sleep states (but do not teach or suggest automated behavioral therapy for insomnia) include:                1) Blanchet et al. U.S. Pat. No. 5,154,180 (system to automatically determine sleep stage using an EEG);        2) Conlan U.S. Pat. No. 5,197,489 (system that can detect wake and sleep using an activity (or movement) monitor (actigraphy));        3) Lavie U.S. Pat. No. 5,280,791 (system that can determine the sleep state of a person by analyzing cardiac EKG R-R intervals);        4) Ogino U.S. Pat. No. 5,479,939 (device that can be used to determine between wake and sleep through a non-contact body movement sensor in bed);        5) Conlan U.S. Pat. No. 5,573,013 (system that can detect wake and sleep using an activity monitor (actigraphy));        6) Sackner et al. U.S. Pat. No. 5,588,425 (system that can be used to discriminate between sleep and wake in a monitored subject based on systolic upstroke times in a pulse oximetry waveform);        7) Ogino U.S. Pat. No. 5,724,990 (device that can be used to distinguish between wake and sleep through a non-contact body movement sensor in a bed or seat);        8) Rapoport et al. U.S. Pat. No. 5,732,696 (system that uses multiple physiological signals (EEG, EMG and EOG) to score sleep);        9) Kaplan et al. U.S. Pat. No. 5,813,993 (to the present inventors) (system that tracks the state of a subject along a continuum of alertness, drowsiness, sleep, unconsciousness or anesthesia from a single channel of spontaneous EEG);        10) Bader U.S. Pat. No. 5,846,206 (system that estimates a person's wakefulness using a stationary pressure sensor in contact with that person's body);        11) Ogino U.S. Pat. No. 5,902,255 (device that can be used to distinguish between wake and sleep through a non-contact body movement sensor in a bed or seat);        12) Halyak U.S. Pat. No. 5,928,133 (device for waking a person within a preset time range when the subject is, for all intents and purposes, already awake, using general technologies such as the use of “physiological monitoring means” or “measured electrical resistance” or “monitoring a bodily electrical property”);        13) Pardey et al. U.S. Pat. No. 5,999,846 (“insomnia or vigilance monitor” using an electrical signal from a subject (EEG or otherwise) over a period of epochs, method for assigning a sleep stage type to each epoch using a neural network to determine wake and sleep in order to generate a hypnogram, a method for analyzing the hypnogram to generate a summary index of sleep quality and a method to display summary index of sleep quality based on the hypnogram;        14) Dimpfel U.S. Pat. No. 6,157,857 (system for sleep staging using the EEG);        15) Baumgart-Schmitt U.S. Pat. No. 6,272,378 (system to automatically generate a sleep stage classification using a single frontal EEG derivation using a device that stores a set of features (FFT based) from the incoming data (as a method of compression) and then analyzes these features to determine sleep stages using a neural network);        16) Goor et al U.S. Pat. No. 6,322,515 (system that is capable of determining sleep and wake by monitoring and detecting changes in peripheral arterial tone);        17) Van der Loos et al. U.S. Pat. No. 6,468,234 (sensor sheet that is laid on top of a conventional mattress for measuring the sleep quality of a subject); and        18) Levendowski et al. U.S. Pat. Nos. 6,496,724, 6,625,485 and U.S. Publication No. 2002/0183644 (a system that quantifies the EEG along an alertness continuum).Any of the above passive methods/devices for wake/sleep determination can be used in the practice of the present invention.        